Transmission of digital data is typically accomplished from point to point by modulating a sine wave utilized as a carrier wave through modification of one or more of the characteristic properties of the wave amplitude, frequency, and phase.
Amplitude modulation of sine waves has classically been implemented by directly varying the amplitude of the sine wave as a carrier wave in relationship to the source to be transmitted. A typical signal sine wave is characterized by its amplitude, frequency, and phase. Sine waves are used to transmit data over a host of different media. For amplitude modulated (AM) radio, the broadcasted carrier (sine) wave is modulated with voice and a simple AM receiver can separate the voice from the carrier signal with a diode, amplify the voice and play it through a speaker. AM radio suffers from signal noise byproducts that limit the signal range, quality, and reliability. Typically, modulation or other changes to a pure sine wave will cause byproducts including harmonics, side band, reflections, and electromagnetic interference.
Direct modulation of sine waves as carrier waves produces significant noise that is difficult to filter. Frequency modulation techniques have typically been implemented by encoding information in a sine wave as a carrier wave by varying the instantaneous frequency of the wave. Phase modulation techniques have typically been implemented by encoding information on a sine wave as a carrier wave by variations in the instantaneous phase of the carrier wave.
Hybrid modulations schemes have been developed and include QAM, SM, and SSB. These hybrid modulation schemes established improved data transmission but still suffered from significant noise and other modulation byproducts that reduce the actual transmission rates and use excess spectrum resources.
Accordingly, improvements are sought in wave modulation encoding of data.